Bit control for percussive tools



Dec. 24, 1946. Q Q w 2,413,273

BIT CONTROL FOR PEI iCUSSIVE TOOLS Filed March 27, 1945 a Q/ein 676027062 6 T SmdL.

Patented Dec. 24-, 1946 2,413,273 BIT CONTROL FOR PERCUSSIVE TOOLS Glenn C. Wilhide, Towson, Md, assignor to The Black and Decker Man corporation of Maryland ufacturing Company, 21.

Application March 27, 1945;. Serial No.. 585,146

3 Claims.

This invention relates to an operating handle for high ower and high frequency impact power hammers or percussive tools, in which the vibration is excessive and the handles now available are relatively short lived due to crystallization resulting from the vibration to which they are subjected. Also the vibration of the bit is transmitted to too great an extent through the handle to the operator.

The objects of this invention are to substantially eliminate the transmission of the vibration of the hammer to the handle, and this elimination will not only relieve the operator and allow him to improve his work, but it will add life to the handle and consequently greatly reduce the cost of maintenance of such handles.

This invention is an improvement over the handle shown in Patent Number 2,328,201 in which some of the objections noted above were discovered, and by this invention, corrected.

Although the invention is illustrated in connection with a drill, it may be used with driven tools such as bolt and rivet removers, chisels, punches and the like, which are driven by any type of hammer.

Another object of the invention is to construct the parts simply so that they can be readily assembled and replaced if need should arise, without special tools or skill in such assembly and replacement.

Other objects and advantages of the invention will be apparent from the following description and the accompanying drawing forming a part hereof and in which:

Figure l is a side elevation of a bit holder and a drill bit therein, the same being of the type used with electric and other portable power hammers, the illustration including an operating handle attached directly to the bit holder shank and indirectly to the bit.

Figure 2 is a similar View on a reduced scale of an electric hammer equipped in accordance with Figure 1.

Figure 3 is an enlarged fragmentary vertical sectional view of the handle and holder connectlon.

Referring to the drawing by numerals each of which is used to indicate the same or similar parts in the difierent figures, the construction shown comprises a tool holder I, having a drill bit 2 and an operating handle 3 in their normal operating relation.

The tool holder I in the form shown comprises a socket member 4 and a shank 5 extendlng upwardly from the socket. The tail 6 of the bit is seated in the tapered bore 1 in the socket l and the socket is provided with a transverse aperture 8 through which a suitable implement may be inserted to loosen the bit. When the bit is thus attached to the holder the bit and holder are rigidly connected.

The upper end of the holder shank 5 is reduced at 9 to fit in the nose of the hammer in accordance with the usual practice. In the form shown, the tool holder shank is shouldered peripherally at ID at the bottom of said reduced portion 9, the details'above described being regular practice.

Important difiiculties incident to the operation of the prior art tools of this general type are found to be due to the transmission to the handle and hence to the hands of the operator of the vibrations and the heat due to the impact of the hammer, with the harmful results in the way of the deterioration of the handle by crystallization and loss of efficient control due to weariness and undue heating or burning of the hands.

The present invention is found to reduce and practically eliminate these difilculties.

Anv important feature of this invention on which the result attained is largely dependent resides in the provision of a connection of the operating handle to the bit either directly or through the tool holder, such connection giving a Control of the bit or drill which is suiilciently positive for accurate placement and direction of the holes or work and at the same time providing clearance, reduction of contact and lost motion between the handle and bit sufficient to reduce or preventing transmission of vibration due to the hammer impact, and to similarly reduce or prevent the passage of heat by conduction from the bit to the handle and hence to the hand of the operator.

To this end the tool holder or shank which is rigidly attached to the bit is provided at any suitable point, most conveniently above the socket 4 with a series of splines l2 and intermediate grooves I3 between the splines, which, in the form shown, are substantially parallel to the axis of the holder and bit.

For co-operation with the tool holder and particularly the splines l2 and grooves IS, the drawing shows the handle 3 provided at its inner end with a collar M which encloses or encircles the tool holder shank immediately above the socket member #3, said collar I4 having its central aperture 15 formed. with alternate inwardly disposed splines and grooves which receive and enter respectively the splines l2 and grooves I 3 on and in the shank 5. It is important that there is considerable clearance between collar l4 and holder I and particularly between the interengaging splines of the collar and holder and as a consequence there is a considerable lost motion between the handle and the holder and the bit therein so that the handle is not in any sense rigid with the tool holder l or with the bit 2. The engagement is, however, sufficiently positive to give accurate direction of the bit by the handle and accurate placement and direction of the holes or other work, with reduction and breakage of contact between the bit and holder in operation. The splines l2 on the tool holder are in the preferred form of the invention shown of not much greater axial length than the width of collar M,

The above construction is illustrated in the patent referred to. It has been found in the use of the construction, shown therein, however, that the washer and sleeve above the handle collar were subject to crystallization and failure.

In the present invention, the washer and sleeve have been replaced by two opposed spring collars l6 and I1, and these collars have surrounding their sleeve portions I8 compression spring IS. The shank has an enlarged portion 20 for spring collars l6 and I1 which is grooved at 2| forming an abutment 22, for spring ring 23 which is placed in this groove 2| to hold spring collar I! in its longitudinal position on the holder shank 5.

In the form shown in Figures 1 and 3 the tool holder is provided beneath the handle collar M, with a shoulder or abutment 24'formed at the upper end of the socket or otherwise positively related to the shank and the space between the bottom of the spring collar l6 and the top of the shoulder 24 is greater than the width of the handle collar i4 providing for vertical as well as lateral and rotary play of the handle 3 relative to the bit 2 and/or bit holder I and vice versa.

While the connection of the handle to the bit holder or bit is sufficiently positive to give the desired control of the latter for accurate work, bit

2 is thus permitted to have a limited movement up and down or axially and relatively to the handle and there is also a suificient degree of lost motion or lateral and/or rotative yielding of the bit relatively to the handle so that contact between the bit or holder and the handle is great- 1y reduced, there being no continuous and positive contact between the handle collar M of handle 3 and the bit 2 and/or tool holder I and the vibrations are mainly independent of the handle and such as might be transmitted to the handle are largely absorbed by spring l9. Consequently, the tendency to the transmission of vibration and heat from the bit through the handle to the hand of the operator resulting in discomfort, weariness and loss of efficiency on the part of the operator is greatly reduced or almost entirely prevented and with reduction of vibration of the handle the tendency to failure of the handle and the connection thereto by crystallization is greatly reduced and substantially eliminated.

Figure 2 shows the handle 3 and tool or bit holder and bit 2 assembled in operative relation with an electric hammer 25.

What is claimed as new and is desired to be secured by Letters Patent is:

l. The combination with a bit holder for percussive tools comprising a handle having a collar thereon, the holder fitting loosely in said collar, said holder and collar having means to limit relative rotation therebetween, said holder having resilient means above said collar to resiliently suspend the holder in the collar and the holder having an abutment below the collar located to permit free limited upward movement of the holder in the collar, said resilient means comprising a compression spring and opposed collars on the holder above the handle collar, with the spring therebetween, said holder having a groove extending cercumferentially therein and a spring ring in said groove to limit the upward movement of the upper of said opposed collars,

2. The combination with a bit holder for percussive tools comprising a handle having a collar thereon, the holder fitting loosely in said collar, said holder and collar having means to limit relative rotation therebetween, said holder having resilient means above said collar to resiliently suspend the holder in the collar and the holder having an abutment below the collar located to permit free limited upward movement of the holder in the collar, said resilient means comprising a compression spring and opposed collars on the holder, the lower one bearing on the handle collar, and means on the holder to limit the upward movement of the upper of said opposed collars, the spring being between said opposed collars.

3. The combination with a bit holder for percussive tools comprising a handle having a collar thereon, the holder fitting loosely in said collar, said holder and collar having means to limit relative rotation therebetween, said holder having resilient means above said collar to resiliently suspend the holder in the collar and the holder having an abutment below the collar located to permit free limited upward movement of the holder in the collar, said resilient means comprising a compression spring and opposed flanged collars on the holder above the handle collar, with the spring surrounding the opposed collars and bearing on the collar flanges, and means on the holder to limit the upward movement of the upper of said opposed flanged collars.

GLENN C. WILHIDE. 

